This is a water filter from RBAYSALE. It comes in a pack of 10, but 5 have been used, so there are 5 remaining. Retail Price: 3328 yen ※The following is a copy and paste of the official product description. Please note that there are only 5 filters remaining. ・【Product Specifications】Note: Not applicable to Pure Crystal, Catit, Toozey, etc. Before purchasing a filter, please compare the size with your existing item to check compatibility. Filter size: Diameter: 12.6x12.6cm; Inner diameter: 3.5cm; Thickness: 1cm. Applicable to 1.6L/2L/2.4L cat automatic water dispensers. ・【Great Value】High-quality water softening filters, individually packaged for hygiene. ・【How to Use】Easy for anyone to replace. Before use, rinse the filter with water for 3-5 minutes to remove carbon powder and dust. Place the non-woven fabric side of the filter facing up, align the convex side of the filter with the corresponding slot, and set it in the water dispenser. It is recommended to replace the filter every 1-2 weeks. ・【Care】When cleaning the filter, do not use detergent; rinse the surface dirt with water. Especially in summer, insects may appear, so it is recommended to clean the water dispenser and filter, and change the water every 3 days.